In the continuous manufacture of individual articles, a given article characteristic is often sufficiently indicative of the nature of such articles to permit article quality control to be based primarily upon determinations of variations in such article characteristic. By way of example, in the cigarette-making industry, weight measurements are made of individual cigarettes in the course of their manufacture and a signal is provided indicative of standard deviation. A meter or like display device responsive to such standard deviation signal thus provides an index of manufacturing process performance and permits a variety of courses of action to improve the process.